All of Our Exchanges Are by Candle Light
by Mia-Zeklos
Summary: When Izzy first meets Lydia after the attack, she's still on bed rest.


**Author's Notes: I haven't written femslash in literal years, so please bear with me while I shake off the cobwebs. And, of course, let me know what you think!**

When Izzy first meets Lydia after the attack, she's still on bed rest.

The first thing she sees after entering the room is Magnus's back as he sits on a chair near the bed, hunched over it as magic pours out of his fingertips. It's apparent that he's focusing and would rather not be interrupted, so she tries to sneak out and come back later, but Lydia puts a stop to her plans by rising slightly in her bed and calling out, "Alec?"

And that's enough; she's already alerted everyone in the room to her presence, obviously, so she might as well come in. Magnus hadn't even flinched like she'd expected him to so she steps in hesitantly, closes the door and nears the bed.

Lydia looks so much paler like that; when she's not just an image for Isabelle to see on the security camera. The video from the attack had been blurry and it's only now that she sees the real damage. Her hair is still up in the coiffure from the wedding and it's in absolute chaos, but even that seems unimportant, given how ashy her skin looks.

"It's me," Isabelle says and tries not to sound too apologetic. She knows that Alec's been the one Lydia trusts most in the Institute, so it would make sense for him to come to visit. "I'm not sure where Alec is."

It's a lie. She's got a pretty good idea where Alec is – in the Library with Clary, trying to figure out a tracking spell strong enough to track Jace down and get him home – but she's not about to tell Lydia that. She's got enough problems right now and Izzy doesn't have the heart to tell her that Jace had gone away with Valentine in the first place.

"You'll be able to do it, too," Magnus says briskly, leaning back into his chair. "I need someone to reactivate the iratze every now and then."

Isabelle nods and pulls out her stele, taking the hand she's offered. The healing rune is low on Lydia's forearm and it takes one drag of the stele over her skin for one of the bruises under Lydia's left eye to disappear completely.

"That's interesting," Magnus hums, apparently to himself, and Lydia's gaze strays to him. For the first time since Isabelle's entered the room, Isabelle sees something other than apathy in her eyes.

"What is?" she croaks and Isabelle tries to imagine what the last twelve or so hours have been like for her. She doubts that Lydia and Magnus have got any shared interests to talk about apart from portals and she feels vaguely as if they're both grateful for someone else's presence.

"Alec's runes don't work half as well," Magnus explains. "It's as if–" he cuts himself off abruptly and a strange smile flickers over his face. "Oh, never mind. Do you mind being left alone for a while?" he turns to Lydia first. "Isabelle here will watch over you in the meantime. You know what using too much magic is like." He grimaces slightly at that. "I always need sugar afterwards."

And with that, he unceremoniously turns his back on them and is out of the door before Isabelle can even ask what Lydia's treatment consists of.

"Warlocks are so weird," Lydia says pensively as soon as they're alone and Isabelle finds it in herself to laugh. It's rare for Lydia to sound so unguarded; as if her armour's slipped away to reveal the girl that had been so enthusiastic about everything new on the day she'd first arrived in the Institute.

"That's just Magnus," she confides in her, even if she's not sure if that would be a comforting thought or not. "They're not all like that."

"What do you think he meant with that?" Lydia still seems a bit confused and Isabelle can't really blame her: not only has she lived a mostly Downworlder-free life until now; she had a concussion to top it off, too. "About the runes; he had a point. I definitely feel much better now."

Isabelle can feel a theory coming up but manages to filter herself before spitting it out – it wouldn't do to burden Lydia with anything she wouldn't be able to handle in her current state, or possibly ever, but she files it away to analyse in her own time. She is a scientist, after all.

"I'm glad," she says instead, squeezing Lydia's hand gently. "I'm sure that you'll be back on your feet in no time at all."

Lydia just gives her a tired smile but doesn't argue and Isabelle's glad for that, too: she rarely lies just for the sake of making someone feel better and she wants to make sure that Lydia knows that.

She isn't sure why it matters so much. After all, she'd met Lydia about a fortnight ago and she'd spent the bigger half of that time hating her, but in the last few days – when she'd tried to connect the words 'Lydia' and 'sister-in-law' and had realised that they might have to start getting along soon – something had changed.

But now? Isabelle is finally able to look at things from the outside and it occurs to her just how many sacrifices Lydia has made for the Lightwood family already.

"I'm sorry," she adds. "You shouldn't have been involved in all of this in the first place."

"I don't regret coming here," Lydia shrugs. "It could have gone more smoothly, I'll admit that, but I'm glad I met you."

"Me too," Isabelle says, and is surprisingly unsurprised to find that she means it.

She goes to find Magnus afterwards – her speciality tends to be dead bodies, not girls with concussion – and she finally finds him in the kitchen, drinking something in a tall cocktail glass.

"What is that?" she asks in disdain and he only shrugs in response.

"A piña colada," Magnus says. "I told you I need sugar. Hey!" he shouts when Isabelle plucks it out of his hand and pour it down the kitchen sink. "What was that for?!"

"You need sugar, not to get drunk," she snaps and hands him a cupcake from the fridge. "You can't treat Lydia if you're drunk."

"Warlocks don't get drunk," he points out an Isabelle just scoffs. "Not from just one cocktail, anyway. I really did need the sugar and I didn't want to touch the food of the resident Nephilim. Your mother hates me enough as it is."

Isabelle forces herself to think things over for a second and then nods. "I know; I'm sorry." He'd never threaten Lydia's life, Isabelle is sure of that. "And my mother doesn't hate you, she just–"

"-would like me better if I was dead," Magnus finished for her. "It's quite all right, dear. I don't expect her to approve of me. And if she ever does, I'd worry about what I've turned into."

This time, Isabelle finds it in herself to smile sincerely for the first time in days; but then again, Magnus usually has that effect on people. Maybe, just maybe, she thinks, they can find a way out of the dark; maybe they'll manage to figure it out.

 **o.O.o**

"I can't believe you didn't tell me," Lydia says instead of 'hello' when Isabelle comes in her room less than a week after they'd first met after the attack.

It's just the two of them. Magnus's help wasn't as vital now and he'd gone back to his duty of strengthening the wards when needed and protecting his own kind from Valentine's newly created Shadowhunters. Isabelle's aware that he still spends most of his time in the Institute, though – Maryse never tires of complaining about the apparently outrageous amount of money he's asking for when his help is required.

Isabelle also has the sneaking suspicion that he always evaporates from Lydia's room as soon as he hears her approach.

"Didn't tell you what?" she asks carefully, seating herself on the edge of the bed.

"About Jace," Lydia says and sits up, leaning back into her pillows, frowning at the uncharacteristic lack of balance. Isabelle had already been informed that too many healing runes could do that to you and it's clear that Lydia's irritated by it. "He's gone with Valentine and I didn't evenknow."

"How– Alec," Isabelle sigh in resignation. Of course Alec's told her. He's her brother and she loves him, but his bedside manner really is abysmal. For a second, Isabelle imagines what his visits must have been like: mostly reports, she's sure, because he'd decide that Lydia wanted all the information about what was happening while she was still on bed rest. And knowing Lydia, that's precisely the truth – she and Alec are so similar, it's kind of endearing and rather annoying at the same time. Alec on his own had been a handful, but with a partner in crime, he's an absolute nightmare to deal with. "I didn't want to worry you; you had so much going on anyway. He shouldn't have–"

"Yes, he should have," Lydia cuts her off, voice firmer than Isabelle had expected. "We're trying to– Never mind."

"Are you two up to something?" Isabelle asks suspiciously and narrows her eyes, even more so when Lydia's expression gets a little defensive. Nowshe's the one that looks like she has news she doesn't feel like delivering. "Don't get me wrong, but the last time the two of you plotted things on your own, I almost ended up being stripped from my runes."

Lydia laughs at that – a deep, genuine laugh that takes Isabelle's breath away – and it's the most ridiculous thing ever, because she's been trying to get her to laugh for weeks and now she's finally managed it with a joke at her own expense.

Isabelle can feel her resolve strengthen – she'd do practically anything to get that reaction out of her again.

 **o.O.o**

A few days after that, Lydia is cautiously allowed to go back to her job. No field missions – Magnus had been adamant about that – but her usual documentation-related duties are okay. It's clear that she'd been missing this, because all of a sudden she's nowhere to be found.

Isabelle isn't worried – she knows perfectly well that Lydia is capable of handling herself – but she'd been promised a picnic.

"Is Lydia here?" she asks upon entering the library, her eyes finding Clary and Magnus immediately. Two pairs of bloodshot eyes struggle to focus on her and Isabelle, feeling courageous, adds, "And where's Alec?"

The search for Jace had been altered to low priority on a Clave meeting two days ago, courtesy of the Inquisitor herself. It's easier to weaken Valentine's forces before attacking him personally, they insist, and ever since then the habitants of the New York Institute had doubled the efforts with their own search.

Clary's not taking it well – she looks like she hadn't slept in about a week – but Magnus isn't much better. He's had his nose buried in the Book of the White for days now and nothing has turned up yet, but he doesn't stop trying. Isabelle had agreed to said picnic because she'd felt that she wouldn't be able to handle the general atmosphere of despair much longer.

"They left together about an hour ago," Clary croaks, taking another sip of her coffee. "Why?"

"Lydia said we could– Never mind, I just– where did they go?"

"In Robert's office," Magnus says and despite how tired he is, he manages a little smirk. Isabelle nods and looks away, strangely embarrassed when he shouts 'Have fun!' at her retreating back as she leaves.

Her father's office is three doors away from the library and there are voice floating out of it, as if there are about thirty people arguing inside.

As usual, it turns out to be just her family. Isabelle winces and opens the door abruptly, which is the only way to catch them all red-handed.

Everyone quiets down for a moment, but it's enough for her to take in the scene that welcomes her. Her father is sitting in his chair behind the desk, looking like he'd rather be anywhere else on the planet. Her mother is standing up, eyes fixed on the door and Alec and Lydia are sitting on the couch.

"What's going on here?" she asks and her mother huffs before turning to Alec.

"We'll talk later," she says and Lydia opens her mouth to protest, only to have Alec stop her by putting a hand on her wrist.

"Later," Lydia echoes after what seems to be a short internal struggle and turns on her heel to head for the exit. Alec doesn't move from his place – but then, Isabelle hadn't expected him to – and Lydia discreetly closes the door as she steps out of the office.

To her own surprise, the first thing that comes out of Isabelle's mouth is, "Thank you."

Lydia stops in her tracks and raises her eyebrows. "What for?"

"I don't know what you're doing and I'm honestly not sure I want to know," Isabelle says as they walk down the corridor, "but you're distracting my family from the elephant in the room. If they focus on that and not on the fact that Jace is missing, we're probably going to get much more efficient at looking for him."

Lydia's tentative smile lights up her face. "I do what I can," she says, expression as earnest as ever. "You know, I don't have a family back in Idris and these last weeks you've been the closest I could get to having one again, so thank you."

This is the point where Isabelle decides that this is it; this is the moment everything's been building up to. She feels the realisation flicker through her mind; the way her runes had always worked better than anyone else's when it came to Lydia and how she'd known ever since then that something had changed and had taken a turn she'd never forget.

When Isabelle leans in to kiss her, it feels overdue and just right all at once.

They're in the middle of the Institute; anyone could walk past them. It would be typical of Lydia to pull away now and declare that this is a very bad idea, but she doesn't.

This suits Isabelle perfectly, come to think of it. She doesn't plan on letting her go anywhere in the near future, but she does pull away long enough to say, "Don't worry. If you don't have a family, you can always borrow mine."

 **o.O.o**

Weeks pass and all of a sudden, things change – Jace's retrieval becomes top priority once again and everything in the Institute is– different. Isabelle can't put her finger on it, but there's a certain shift of power that she can easily spot but can never quite understand.

That is, until the hours after they got Jace back.

He still looks shell-shocked and not entirely sure if he's actually home, but Isabelle allows Alec to take care of that. She sees him approach his parabatai and then watches them as they leave. Lydia detaches herself from Alec's side, where she'd been in the last week or so and comes back to Isabelle, where she'd been during the battle.

"How did the two of you manage that?" Isabelle asks curiously. "I didn't think the Clave would let you go through with this mission."

"They didn't have much of a choice," Lydia says with a mischievous look in her eyes that Isabelle has come to love; one that always lets her know that she's definitely up to something. "Come, I'll show you."

Mystified, Isabelle follows her up the stairs and into her father's office. Except it isn't, really. The sign saying 'Head of the Institute' still hangs above the door, but the name Robert Lightwood has been removed from it and two names have been squished in its place.

Lydia Branwell and Alexander Lightwood.

"We did it," Lydia says, clearly unable to hide her enthusiasm. Isabelle had noticed that about her recently; once Lydia focuses her mind on something, there's no letting it go, and especially not if it's something that's important to her. "We kept the Institute!"

"So you're staying." It's not a question; it's more of a statement and Isabelle feels as if an enormous weight has been lifted off of her shoulders. It's a lot to take in for just one day – they'd been allowed to go and search for Jace, had then actually succeeded in finding him and now there was this.

Somehow, among the hectic plans for Jace's rescue mission and the rare moment she'd been allowed to spend alone with Lydia, Isabelle had vaguely realised that it all had an expiration date. She knew that Lydia would have to leave eventually – she had more than enough to deal with in Idris. And now that they'd put an end to that, Isabelle's heart beats three times lighter than it had hours ago.

"I'm staying," Lydia shrugs and the smile still lingers in her eyes and her voice. "Sharing your family doesn't sound half bad, you know. They're all a bit of a handful, but–"

They never get to hear what more she's got to say on the matter because Isabelle swallows the words with a kiss.


End file.
